If you travel from low elevation to high elevation for a race, brace yourself for some notable side effects, including feeling short of breath and seeing your speed and endurance suffer. The good news is that given an appropriate period of time, your body can acclimate to that new elevation.
In general, the longer you have to acclimate to a major increase in elevation before a race, the better. Current clinical research suggests that 10 days is the shortest "ideal" period for acclimating, although even if you only have a couple of days to acclimate you can still take several tangible actions to support your body and improve your overall performance.
What Altitude Does
Every person has a unique physiological response to an increase in altitude, and for the healthy and fit, those changes might not be immediately obvious at rest. But once you strap on your shoes and head out for a training run or to run a race, you'll probably start to notice some of the changes happening in your body.
As noted in an article published in the March 2016 issue of Sports Health, just a few of the short-term issues that can affect athletic performance include increased heart rate and blood pressure; shifts in hormone and blood nutrient levels; dehydration; mood changes; and decreases in cognitive, motor and sensory function. Exposure to unusual altitudes also increases your risk of altitude-related illnesses such as high-altitude pulmonary or cerebral edema.
The researchers go on to note that the ideal acclimatization period depends on several factors, including your individual response to altitude, what altitude you normally reside at and the altitude to which you plan to ascend.
The Ideal Acclimatization Period
So how long is the ideal acclimatization period for intense exercise at higher altitudes than you're used to?
In the already mentioned Sports Health article, researchers noted that of the three common protocols for acclimatizing to altitude, "live high, train low" may be the best for enhancing endurance performance. In this protocol, athletes train at lower elevation so they can maintain their workout volume and intensity without ill effects, but do their recovery at higher elevations to benefit from the physiological adaptations this causes.
But this protocol takes a significant chunk of time, requiring you to accumulate 300 to 400 hours at altitude — which usually works out to a period of at least 20 days.
Your body can and does begin to adapt to the new altitude in less time. For example, in a narrative review published in a 2018 issue of Frontiers in Physiology, researchers describe the habit of European coaches using slightly shortened stays at higher altitude (10 to 14 days), based on empirical evidence that these trips benefit their athletes. They also note that physiological adaptations to higher altitude nearly plateau after a two-week acclimatization period.
And in a 2017 issue of the International Journal of Exercise Science, researchers related their studies of a very small group of volunteers (eight people) in a 10-day altitude training camp. They stated that cardiovascular changes can occur at altitudes as low as 1,828 meters (about 6,000 feet), and in as short a period as 10 days.
If You're on a Schedule
Of course, even a 10-day to two-week stay won't be within the reach of many athletes — especially if you're paying your way to run in a recreational race. The authors of the Frontiers in Physiology review go on to recommend that if you only have access to altitude for a very short period before your competition, one of the better approaches may be to arrive the day before the competition and check out the course, then sleep at low altitude before returning to altitude the next day.
This is based on findings from another study that was originally published in 1985, but was republished in a November 2017 issue of the Journal of Applied Physiology. In the newest publication, the authors note a new, noteworthy conclusion that "athletes who cannot arrive at altitude with adequate time for complete acclimatization can choose the short-term arrival strategy that best fits with the logistics of their travel."
Have you noticed the conditional language — may, might and so on — being thrown around? That's because, again, each person has a distinct individual response to increases in elevation, and exercise researchers are still hunting for the ideal solution to shorten the required acclimatization time and improve performance for visitors to a higher elevation.
Other Issues to Consider
Even if you can't set yourself up for a two-week training camp in advance of your race, there are some tangible measures you can take to help yourself adapt to your new elevation before the event begins.
The first is planning your schedule to allow yourself adequate rest time, both during your trip to the new locale and in the day(s) leading up to your event. Although scientists still haven't deciphered the deepest mysteries of exactly why or how, they acknowledge that getting enough sleep can have a profound effect on your body's performance.
Along the same vein and working under the assumption that you'll fly to reach your destination, the second very tangible thing you can do is shift your schedule beforehand to minimize jet lag. This can mean incrementally shifting not only your sleep schedule but your meal times, also, to more closely align with the eating and sleeping schedules at your destination.
Another thing to do is watch your hydration levels. Not only can a sudden increase in elevation prompt increased urine output, but you also lose more moisture through your lungs at higher elevations.
If you know you won't have time for a prolonged acclimation period at your destination, give yourself as much time as you can — and consider doing a training run or two at similar elevation if possible. You'll get a better idea of how you can expect your body to perform and — if this is a "bucket list" or life landmark event you're training for — that experience might motivate you to prioritize finding the time and money to allow yourself at least 10 days of acclimation time.
Even if those exposures to exercise at altitude don't change your overall travel plans, knowing how your body responds to that challenge can help you prepare, both mentally and physically, for your race.
Finally, take the time to chat with your doctor about any extra precautions you should take before exerting yourself at a high altitude, especially if you're not going to have time to acclimate beforehand. If any medications, medical conditions or other risk factors might present a problem, it's much better to have a plan in place for managing them beforehand — and understanding the probable effects of that new elevation can help you set realistic expectations for your performance.
- Sports Health: "Athletes at High Altitude"
- International Journal of Exercise Science: "The Effects of a 10-day Altitude Training Camp at 1828 Meters on Varsity Cross-Country Runners"
- Frontiers in Physiology: "Preparation for Endurance Competitions at Altitude: Physiological, Psychological, Dietary and Coaching Aspects. A Narrative Review"
- Journal of Applied Physiology: "Short-Term Arrival Strategies for Endurance Exercise Performance at Moderate Altitude"